在sql server

Question

我将此表格命名为expenses，其中包含以下字段refnum, transdate, transtype, transcategory, amount

此表包含以下数据

refnum | transdate  | transtype | transcategory |     amount 
 1     | 10/10/2015 |  cash-out |     null      |    5000.00 
 1     | 10/10/2015 |  cash-in  |     null      |    3000.00 
 1     | 10/10/2015 |  cash-in  |     null      |    1000.00 
 2     | 10/10/2015 |  cash-out |     null      |    5000.00 
 2     | 10/10/2015 |  cash-in  |     null      |    3000.00 
 2     | 10/10/2015 |  cash-in  |     null      |    2000.00
 3     | 10/10/2015 |  cash-out |     null      |    5000.00
 3     | 10/10/2015 |  cash-in  |     null      |    5000.00

问题是：是否有可能根据transtype and refnum

获得金额余额

我有这个问题：

SELECT 
    A.refnum, A.transtype, A.amount,(A.amount-B.amount) as balance 
FROM 
    expenses AS A 
INNER JOIN
    expenses AS B ON A.refnum = B.refnum 
WHERE
    A.transtype = 'cash-in' 
    AND B.transtype = 'cash-out' 
    AND (A.amount - B.amount) > 0

我很困惑，如果cash-in与cash-out的数量完全相同，我认为此查询很好，但问题几乎所有cash-in与cash-out的数量不同{ {1}}，希望你们明白我的要求。

我需要的查询只会显示refnum的{​​{1}}。

有可能吗？

Answer 1

就像尼克说：

使用conditional with aggregated methods

另一个example

SQL Fiddle Demo

• group by会将您的数据分成不同的组，在这种情况下，每个引用句柄的组（1,2,3）GROUP BY
• conditional SUM：正常的SUM(amount)会为您提供上面定义的整个群组的总和。但并非所有金额都是积极的。因此，您使用CASE语句将amount更改为-amount WHEN transtype='cash-out'

SELECT 
    refnum, 
    SUM(CASE 
            WHEN transtype='cash-out' then -amount 
            ELSE amount 
        END)  as total
FROM expenses 
GROUP BY refnum

修改

供您参考，这是一种使用CTE和Join

的方法

• CTE或Common Table Expressions：允许您创建子查询，以便在其他查询中使用它。就像创建一个时态表一样，你可以选择或加入该结果。
• 在这种情况下，我创建了两个表cash_out和cash_in，每个表都包含每个引用句柄的总和值。
• 在我写完之后，我意识到如果一个refnum没有cash_in或cash_out这不会起作用。所以我添加了另一个子查询以包含所有refnum，并以这种方式执行left join，如果不是数据，则连接仍将起作用并添加0。
• ISNULL(variable,0)：如果variable则返回variable <> null，否则返回0

SQL Fiddle Demo

WITH ref as (
    SELECT DISTINCT refnum
    FROM expenses
),
cash_out as (    
    SELECT A.refnum, SUM(A.amount) balance 
    FROM 
        expenses AS A 
        where A.transtype = 'cash-out'
    GROUP BY A.refnum
),
cash_in as (
    SELECT A.refnum, SUM(A.amount) balance 
    FROM 
        expenses AS A 
        where A.transtype = 'cash-in' 
    GROUP BY A.refnum
)
SELECT cin.refnum, (ISNULL(cin.balance,0) - ISNULL(cout.balance,0)) as total
FROM 
   ref r LEFT JOIN
   cash_in cin on r.refnum = cin.refnum LEFT JOIN
   cash_out cout on r.refnum = cout.refnum